Abradant sheet material and process of its manufacture



Patented Apr. 16, 1935 V 1 UNITED {STATES Lawrence, E. Bar-ringer, signorto General Elect tion of New, York No drawing. Or! 1926, Serial No.

This application is a division of my application Serial No. 152,486, filed December 3, 1926, relating. to the manufacture of abradants, such for example, as grinding wheels, whet-stones, razor "hones, drills, sand paper,'and in general articles used for grinding or abrading purposes. As claims specific to a grinding wheel have been allowed in this prior application, I have made claims herein to abrasive sheet material, as for example, paper or cloth coated with comminuted 1 abrasive and embodying as a novel feature, a

binder of resinous material made by the interaction of polyhydric alcoholzand'polybasic acid.

A binder for abrasive. articles should not only give the article mechanical strength but should have such physical. properties that the abrasive material can be used without deterioration of it'scutting property. For example, the binder must not clog or gum the abrading surface whenthe surface is subjected to frictional heating during use.- The binder must retain its bonding strength at high temperatures so as not to permit frictional disintegration of the surface layer. For some abradants, as in sand paper,- elasticity of the binder is desirable. For some abradants immunity to moisture is important. The binder" should not readily decompose orcarbonize when heated.

I have found resins of the polyhydric alcoholpolybasic acid-class to have the special physical properties required for binders high grade abrasive materials. These resins not only possess a high degree of strength and elasticity but are able to withstand high temperatures without decomposition. They do not'clog-the surface layers of abradants, made by their use 'as binders. My invention comprises both new abradant compositions and a new method of fabricating the same.

In carrying out my invention a comminuted abrasive material, such as alundum, carborundum, emery, garnet, or the like is mixed with a suitable amount of polybasic acid-polyhydric alcohol resin of the class described in Callahan Patents 1,108,323 and 1,108,330 of August 25, 1914. This-class of resins will be referredto in the appended claims generally as alkyd resins. Alkyd resins include all those complexes resulting primarily'from the interreaction of, a polyhydric alcohol, such as glycerol, and a polybasic. acid, such as phthalic anhydride. I Alkyd resins areconvertible by heating from a fusible state (A-stage) to a. very-tough, hard, inert, and non-fusible state (C-stage). In an intermediate state (B-stage) the resin is less ET MATERIAL OF ITS MANUFACTURE :inal application December 3, 152,486. v plication October 26, 192

4 Claims. (01. 51-280);

PATENT OFFICE AND rnocnss Schenectady, N. n, as-

rlc Company, a corpora? Divided and this ap- 9, Serial No. 402,801

inert. In the B-stagethe resin will'notfuse but softens somewhat when heated. The A-stage resin is readily soluble in cold acetone. The B-stage and C-stage resin can be rendered soluble by heating with a solvent at sufficiently elevated 5 temperatures. Preferably, but not necessarily, the resineis associated with a plasticizing agent, such for example, as indene, indene polymer, tricresyl phosphate, diethyl phthalate, glycol benzyl benzoate; triacetin, or the like.

The alkyd resin may be mixed with a suitable amount of plasticising agent,'say ten per cent, at any of its conversion stages. For example, the resin can be incorporated with a solvent by heating the resin, preferably in powdered form, in contact with a solvent to a sufliciently high temperature until the resin structure is altered and solution occurs. Enough of the liquid plasticising agent should'be removed from the resin to permit a solidified product to 'be obtained or else a solid 'plastic'ising agent mayv be used, such as cumar, rosin, ester gum, .a pitch, diphenyl, or even a natural gum.

The resin binder may be incorporated with .the abrasive material in any suitable way soas to get a complete distribution of the resin throughout the mass. For example, the comminuted abrasive may be incorporated with a solution, of the resin in'a suitable solvent, such as acetone, or mixed solvents as acetone, alcohol and benzol or alcoholic solutions of ammonia. Complete admixture may be assured by stirring the mass, as for example, in a heated dough mixer. In other cases the commimited abrasive may be mixed with liquefied resin in a suitable mixing device, preferably at an elevated temperature. By another method the solid resin is powdered, preferably to a fineness which will pass through a 60 mesh" screen, and then mixed with the abrasive. Any of the foregoing methods of mixing may be used.' I do not wish to be limited to these particular methods for any procedure whereby the abrasive and resin particles are brought into intimate contact to form a thorough mixture is satisfactory for the-purpose. When the mixtureis' to be used for coating cloth or paper, I prefer to first coat the paper with a solution or alkyd resin, then; air dry until tacky, apply the grains of abrasive-material and finally bake the whole unt' the grains are firmly set in the resinous coating. The proportion of resin to abrasive will varywith conditions but by way of example, I may state that I have used successfully 60 parts of 55 diacetate,

abrasive, such as alundum, with} parts of resin made from glycerol and phthalic anhydride.

The abrasive and resin mixture may be molded at about 150 C. preferably in steel molds. The

molding mass is held at this temperature for a few minutes, the exact time depending on the size of the mass and other conditions. The molded objects may be cooled in the mold to about 75 C. Thereupon the molded pieces are discharged from the mold and the resin is polymerized without pressure (other than atmospheric pressure) in an oven for a protracted period, say 50 to 150 hours, depending upon the size of the article, at a temperature rising radually from about 75 C. to about 190 C, This heat resen'ce of small amounts of resin does notapp'reciably lower the effect of the abrasive maed States is:

ture comprising a flexting thereon comprising sive material ture comprising a flexting thereon comprisphthalic anhydride resin in a insoluble state, and par bedded in said coating.

facture comprising paper,

treatment or polymerization which is given the articles after thebinderhas been given an initial set by molding, develops to the fullest degree the strength of the resinous bond and therefore the mechanical strength and toughness of the finishedarticle. I

lkyd resin in of abrasive maa coating thereon comprising an a a polymerized state and particles terial imbedded in said co 4. An article of fibrous sheet materia stituted of an alk manufacture comprising a 20 1, a coating thereon conassociated with a. plas- Theflresulting product is strong, moisture-re-' sistant; and can be used under severe service con- 01 resin being in a water resistant,-insoluble state; and particles of abrasive maticizing agent, sai

ditions without gumming or clogging of the sur- 566.: .In fact, this class of resins themselves have an abradant action on cutting tools and it apin said coating.

terial imbedded I LAWRENCE E. BARRINGER. 

